1. Field of the Invention
The present invention relates generally to mercury sorbent inorganic dry compositions and devices incorporating such compositions and specifically to their use to suppress mercury vapor emissions.
2. Background Information
The replacement of incandescent light bulbs with fluorescent light bulbs in order to achieve increased energy efficiency continues to accelerate in home, business, government and academic environments. Government mandates will soon eliminate nearly all sales of incandescent bulbs for routine lighting purposes in the US. While fluorescent light bulbs provide a substantial advantage over incandescent bulbs with respect to energy usage, they contain mercury, which, if released into the air, can pose health risks to exposed individuals. Typical compact fluorescent light bulbs (CFL's) contain approximately 3 to 5 mg of mercury. It has been pointed out that the amount of mercury released into the atmosphere resulting from the eventual breakage or destruction of fluorescent light bulbs represents only a portion of the total mercury contamination in air, the bulk of which appears to result from the burning of fossil fuels such as coal for electrical energy generation. Nevertheless, the health risk to individuals associated with fluorescent light bulbs arises from the potential concentration of mercury vapors in enclosed spaces such as the home or workplace upon breakage. Collection sites for recycling of CFL's and other fluorescent light bulbs afford a particular risk for unwanted exposure to mercury vapor. Individuals involved in the recycling process when in proximity to recycling storage, transport, or processing (for example recovery or disposal) sites are at particular risk. Businesses or organizations housing such recycling sites may incur significant liability as employees, customers or other individuals are inadvertently exposed to mercury vapor.
Recently, methods have been developed to allow the safe transport of CFL's, tubular fluorescent light bulbs, and fluorescent light bulbs of various other shapes. U.S. Patent Application No. 2009/0095133 describes methods and devices for the safe and cost-efficient storage, transport and disposal of mercury containing light bulbs and other mercury containing materials comprising a puncture resistant container having interior element capable of sequestering mercury thus preventing release of mercury vapor into the environment. Mercury sequestering agents are well known to those skilled in the art. They include sulfur, activated carbon impregnated with sulfur as described in U.S. Pat. No. 3,194,629, polymers having free thiol groups such as styrene polymers containing pendent ethane thiol moieties as described in U.S. Pat. No. 4,021,416. Additional examples of free-thiol containing polymers are described in references 4-6. Additional types of sequestering agents are known to complex mercury include activated charcoal, wood char, hydrated aluminosilicate having micro porous structure such as a zeolites and molecular sieves. U.S. Pat. No. 4,534,944 describes a liquid mercury vapor absorbent and suppressant comprising copper ions and thiosulfate ions in water or a water polyol mixture used to immerse mercury. U.S. Pat. No. 4,876,025 describes a liquid mercury vapor absorbent in which the liquid mercury absorbent coats the mercury droplet.
While various liquid absorbents may be effective, they are limited in their use to applications where spillage is not a problem or where the surface of exposure to mercury is relatively concentrated or physically constrained, for example as is the case with droplets of mercury in a container which can be submerged or coated with the mercury absorbing liquid as described in U.S. Pat. No. 4,876,025 and U.S. Pat. No. 4,534,944, that might for example be collected after a spill or in collection of mercury containing dental amalgams and associated fragments obtained during insertion or removal of the amalgams during dental procedures.